Architecture for Computing System Package

ABSTRACT

A method includes forming a reconstructed wafer, which includes forming a redistribution structure over a carrier, bonding a first plurality of memory dies over the redistribution structure, bonding a plurality of bridge dies over the redistribution structure, and bonding a plurality of logic dies over the first plurality of memory dies and the plurality of bridge dies. Each of the plurality of bridge dies interconnects, and is overlapped by corner regions of, four of the plurality of logic dies. A second plurality of memory dies are bonded over the plurality of logic dies. The plurality of logic dies form a first array, and the second plurality of memory dies form a second array.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of the following provisionally filedU.S. Patent application: Application No. 63/137,375, filed on Jan. 14,2021, and entitled “SoIC Technology for New Immersion in Memory ComputeSystem Architecture;” which application is hereby incorporated herein byreference.

BACKGROUND

The packages of integrated circuits are becoming increasing complex,with more device dies integrated in the same package to achieve morefunctions. For example, system packages have been developed to include aplurality of device dies such as processors and memory cubes in the samepackage. In the system packages, device dies formed using differenttechnologies and having different functions can be bonded in both 2Dside-by-side and 3D stacking manner to form a system, which has highcomputing efficiency, high bandwidth, high functionality packingdensity, low communication latency, and low energy consumption per bitdata.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, and 1G illustrate the cross-sectionalviews, perspective views, and top and bottom views of a computing systempackage in accordance with some embodiments.

FIGS. 2 through 14 illustrate the cross-sectional views of intermediatestages in the formation of computing system packages in accordance withsome embodiments.

FIGS. 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, and 17C illustrate thecross-sectional views of computing system packages in accordance withsome embodiments.

FIGS. 18A and 18B illustrate the top and bottom views of computingsystem packages in accordance with some embodiments.

FIGS. 19A, 19B, 20A, 20B, 21A, 21B, 22A, and 22B illustrate thecross-sectional views of computing system packages in accordance withsome embodiments.

FIG. 23 illustrates a perspective view of a die-to-wafer bonding processin accordance with some embodiments.

FIG. 24 illustrates a perspective view of a wafer-to-wafer bondingprocess in accordance with some embodiments.

FIG. 25 illustrates a part of an interconnect structure in a bridge diein accordance with some embodiments.

FIG. 26 illustrates the capacitors in a bridge die in accordance withsome embodiments.

FIG. 27 illustrates an amplified view of the encapsulants in a computingsystem package in accordance with some embodiments.

FIG. 28 illustrates a process flow for forming a computing systempackage in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A computing system package and the method of forming the same areprovided in accordance with various embodiments. The computing systempackage may include three tiers, with the middle tier including logicdies, and the bottom tier and top tier including memory dies.Accordingly, logic dies have shortest paths to the memory dies theyaccess. Bridge dies are in the bottom tier, and are used to interconnectlogic dies. Each of the logic dies thus has maximized access to otherlogic dies and memory dies, without increasing the complexity of thesystem. Also, the scalability of the system is improved due to theadoption of arrays of logic dies, memory dies, and bridge dies. Withthis setting, the computing efficiency may be improved, the bandwidth ofthe system may be increased, and the latency may be reduced due to theclose proximity of the memory dies and logic dies, and the efficientlayout. The intermediate stages in the formation of the package areillustrated in accordance with some embodiments. Some variations of someembodiments are discussed. Throughout the various views and illustrativeembodiments, like reference numbers are used to designate like elements.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, and 1G illustrate the cross-sectionalviews, perspective views and top and bottom views of a computing systempackage 100 in accordance with some embodiments. The computing systempackage 100 includes logic dies, memory dies, and bridge diesdistributed in a plurality of tiers including tier-1, tier-2 and tier-3,which are encapsulated in encapsulant 130, 132, and 134, respectively.Tier-1 may include memory dies MD1 and bride dies BD. Tier-2 may includelogic dies LD. Tier-3 may include memory dies MD3. Logic dies LD performcomputing functions, and the logic dies LD access memory dies MD1 andMD3. In the drawings of the present disclosure, the reference numbers ofdevice dies may start with symbol “LD,” symbol “MD,” or symbol “BD.”Symbol “LD” is used to represent that the corresponding die is a logicdie. Symbol “MDI” is used to represent that the corresponding die is amemory die in tier-1, and symbol “MD3” is used to represent that thecorresponding die is a memory die in tier-3. Memory dies MDI and MD3 arecollectively referred to as memory dies MD. Letter “BD” is used torepresent that the corresponding die is a bridge die. In each of thetiers tier-1, tier-2 and tier-3, the number of logic dies and the numberof memory dies may be more than illustrated. It is appreciated thatalthough three-tier packages are shown as examples, the computing systempackages may include more than three tiers such as four tiers, fivetiers, or more, and the addition tiers may be under the illustratedtier-1, and/or over the illustrated tier-3.

In accordance with some embodiments of the present disclosure, the logicdies LD may be Application Processor (AP) dies, Graphics Processing Unit(GPU) dies, Field Programmable Gate Array (FPGA) dies, ApplicationSpecific Integrated Circuit (ASIC) dies, Input-Output (IO) dies, NetworkProcessing Unit (NPU) dies, Tensor Processing Unit (TPU) dies,Artificial Intelligence (AI) engine dies, or the like.

In accordance with some embodiments of the present disclosure, thememory dies MD1 and MD3 may include Static Random Access Memory (SRAM)dies, Dynamic Random Access Memory (DRAM) dies, wide I/O memory dies,NAND memory dies, Resistive Random Access Memory (RRAM) dies,Magneto-resistive Random Access Memory (MRAM) dies, Phase Change RandomAccess Memory (PCRAM) dies, or the like, or other types of volatile ornon-volatile memory dies. The memory dies may include, or may be freefrom, controllers therein. In the embodiments in which memory dies donot include controller, the controllers may be built in logic dies. Thememory dies may also be in the form of single memory die or pre-stackedmemory cubes.

In computing system package 100, and possibly in each of the tiers,different types of memory dies may be mixed. For example, tier-1 mayadopt one type of memory dies as aforementioned, and tier-3 may adoptanother type of memory dies. All of the memory dies in tier-1 may,however, be of the same type and are identical to each other, and thememory dies in tier-3 may be of the same type and are identical to eachother in order to improve the scalability of the system, and to reducethe thickness of the package (since if different types are mixed, thethickness of the corresponding tier is determined by the thickest type).The logic dies LD in tier-2 may include different types of logic dies,which may include the aforementioned. Alternatively, all of the logicdies in tier-2 may be of the same type and identical to each other.

Tier-1 may include a plurality of memory dies MD1 and a plurality ofbridge dies BD, and may be, or may not be, free from other types of diessuch as logic dies, independent passive device dies, and the like.Tier-2 may include a plurality of logic die LD, and may be, or may notbe, free from other types of dies such as memory dies, bridge dies,passive device dies, and the like. Tier-3 may include a plurality ofmemory dies MD3, and may be, or may not be, free from other types ofdies such as logic dies, bridge dies, passive device dies, and the like.

Each of Logic dies LD, memory dies MD1/MD3, and bridge dies BD mayinclude semiconductor substrates 20A, 20B, or 20C, which may be siliconsubstrates. Interconnect structures 22 are formed on the correspondingsemiconductor substrates 20A/20B/20C, and are used to interconnect thedevices in the corresponding dies. Through-substrate vias 26A and 26Bmay be formed to penetrate through the corresponding semiconductorsubstrates 20 of the tier-1 dies and tier-2 dies, and are used for theinterconnection of the overlying components to the underlyingcomponents. Furthermore, electrical connectors 28 may be formed forbonding to other device dies. Electrical connectors 28 are used for thebonding between the dies in different tiers, and may be metal pads,metal pillars, solder regions, or the like. In accordance with someembodiments, electrical connectors 28 are metal pillars (such as copperpillars), and are in the corresponding surface dielectric layers 30. Inaccordance with some embodiments, surface dielectric layers 30 areformed of or comprise silicon oxide. In accordance with otherembodiments, surface dielectric layers 30 include a polymer such aspolybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like.Throughout the description, the side of semiconductor substrate 20having interconnect structure 22 (and active device such as transistors,not shown) are referred to as a front side (or “face”), and the oppositeside is referred to as a backside (or “back”). Accordingly, depending onwhich sides of the dies are bonded to each other, the bonding may beface-to-back bonding, face-to-face bonding, back-to-back bonding. Forexample, in FIG. 1A, face-to-back bonding is adopted.

Further referring again to FIG. 1A, 1F, or 1G, neighboring tiers arebonded to each other, either through direct metal-to-metal bonding,solder bonding, or hybrid bonding. Hybrid bonding includes bothdielectric-to-dielectric (also known as fusion bonding, in which Si—O—Sibonds may be formed between two bonded dielectric layers).

Underlying tier-1 dies may have an interconnect structure(redistribution structure) 50. Redistribution structure 50 may includedielectric layers 54, 108 and 116, RDLs 106 and 112, and Under-BumpMetallurgies (UBMs) 114. Electrical connectors 142, which may includesolder regions, metal pillars, micro-bumps, or the like, are formed atthe bottom surface of redistribution structure 50.

FIGS. 1B and 1C illustrate a top view and a bottom view, respectively,of the computing system package 100 as shown in FIG. 1A. Thecross-sections of the computing system package 100 may be foundreferring to FIGS. 1A, 1F, and 1G, with FIG. 1A illustrating referencecross-section 1A-1A in FIGS. 1B and 1C, FIG. 1F illustrating referencecross-section 1F-1F in FIGS. 1B and 1C, and FIG. 1G illustratingreference cross-section 1G-1G in FIGS. 1B and 1C. As shown in FIG. 1B,memory dies MD1 and bridge dies BD are illustrated as being dashed sincethey are under logic dies DL. In accordance with some embodiments,memory dies MD3 may be arranged as an array. Logic dies LD may bearranged as an array. Bridge dies BD may be arranged as an array, andmemory dies MD1 may also be arranged as an array. Although 3×3 arraysare illustrated as an example, larger arrays may be formed. Formingdevice dies as arrays has the advantageous feature of high scalability.This is particularly useful for increasing the computing power throughadding more logic dies, memory dies, and bridge dies. As will bediscussed in subsequent paragraphs, the co-operation of the logic diesmay be achieved through sharing memory dies, and interacting throughbridge dies, so that scaling up the system and increasing the computingpower may be easily achieved by enlarging the device arrays.

In accordance with some embodiments, all of logic dies LD are identicalto each other. In accordance with alternative embodiments, some logicdies LD are identical to each other, and are different from other logicdies LD, which are also identical to each other. For example, a firstplurality of logic dies LD may be identical to each other, and a secondplurality of logic dies LD may be identical to each other, and aredifferent from the first plurality of logic dies LD. The first and thesecond plurality of logic dies LD may be laid out in an alternatinglayout, for example, alternating in each of the rows and columns of thearray.

In accordance with some embodiments, each of memory dies MD3 is bondedto, and signally accessed by, one of logic dies LD. Each of memory diesMD1 is bonded to, and signally accessed by, two neighboring logic diesLD, which are also illustrated in FIG. 1G. With this layout, each logicdie may access three memory dies directly without having routing linesin between. This significantly increases the amount of memory accessedby logic dies without increasing the power consumption and latency.

Further referring to FIGS. 1B and 1C, each of bridge dies BD is bondedto, and interconnects, four logic dies LD. Bridge dies BD are used forthe intercommunication of the four connecting logic dies with eachother. For example, bridge dies BD may include conductive lines therein,which directly interconnect each pair of the four logic dies LD. Bridgedies BD may also include networking circuits (and hence may be anetworking-on-chip die), which include switches, router circuits, or thelike, for switching signals between each pair of the four logic dies.Accordingly, through the bridge dies BD, all four logic dies LD mayfunction as an integrated system. Furthermore, each of the logic dies LDis connected to four bridge dies, and hence can route signals from anyof the four bridge dies to the other. Accordingly, all of the logic diesLD may work with each other (through bridge dies BD) to form anintegrated computing system, and to achieve parallel computing. As canbe conceived from FIGS. 1B and 1C, the computing system package 100 canbe scaled up to increase computing power by replicating and enlargingthe arrays of logic dies LD, memory dies MD1 and MD3, and bridge diesBD.

FIGS. 1D and 1E illustrate the perspective views of computing systempackage 100 in accordance with some embodiments, FIG. 1D illustrates aperspective view from top side, and Figure lE illustrates a perspectiveview from bottom side.

FIG. 1F illustrates the reference cross-section 1F-1F as shown in FIGS.1B and 1C. Memory dies MD1 are not illustrated in FIG. 1F since memorydies MD1 are not in the illustrated cross-section. The two logic dies LDconnected to the same bridge die are illustrated, while the other twologic dies connecting to the same bridge die BD are not illustratedsince they are not in the illustrated cross-section.

FIG. 25 schematically illustrates a bridge die BD, which includesbridging structure 34 for interconnecting logic dies LD. In accordancewith some embodiments, bridging structure 34 is formed in interconnectstructure 22 of bridge die BD. For example, interconnect structure 22may include dielectric layers (sometimes referred to as Inter-MetalDielectrics (IMDs)), which may include low-k dielectric materials.Bridging structure 34 may include metal lines and vias, which may extendinto a plurality of metallization layers in interconnect structure 22.The metal lines and vias are interconnected to form a plurality ofelectrical paths 36, with opposing ends of each of electrical paths 36connecting to an electrical connector 28A, which may include a metalpad, a metal pillar, a solder region, or the like. Logic dies LD haveelectrical connectors 28B, which are bonded to electrical connectors28A. Bridging structure 34 may also include digital switches, routers,or the like, which may include the electrical paths, and switches (whichinclude active device such as transistors and control circuits).

Referring back to FIG. 1F, bridge dies BD may also include passivedevices 42/43 such as capacitors, resistors, inductors, or the like.FIG. 26 illustrates an example bridge die BD. In accordance with someembodiments, bridge die BD includes deep trench capacitor 42 and/orMetal-Insulator-Metal (MIM) capacitor 43. Deep trench capacitor 42 mayinclude capacitor electrodes 42B and insulator 42A between capacitorelectrodes 42B, with deep trench capacitor 42 extending into a trenchformed in semiconductor substrate 20, so that the capacitance may beincreased. MIM capacitor 43 may include capacitor electrodes 43B andinsulator 43A between capacitor electrodes 43B, and may be formed in theinterconnect structure 22 in bridge die BD. In accordance with someembodiments, MIM capacitor 43 and the electrical paths 36 (FIG. 25)extend into the same interconnect structure 22 in bridge die BD.

FIG. 1G illustrates the reference cross-section 1G-1G as shown in FIGS.1B and 1C. Bridge dies BD are not illustrated in FIG. 1G since bridgedies BD are not in the illustrated cross-section.

As shown in FIGS. 1A, 1F, and 1G, through-vias 26A are formed in memorydies MD1 and bridge dies BD, and penetrate through the semiconductorsubstrates 20A of memory dies MD1 and bridge dies BD. Through-vias 26Aare used to electrically and signally couple redistribution structure 50to logic dies LD. As shown in FIGS. 1F, and 1G, through-vias 120(through-molding vias) are formed to penetrate through encapsulant 130,and are used to electrically and signally couple redistributionstructure 50 to logic dies LD.

FIGS. 2 through 14 illustrate the cross-sectional views of intermediatestages in the formation of computing system packages 100 as shown inFIGS. 1A, 1B, 1C, 1D, 1E, 1F, and 1G in accordance with some embodimentsof the present disclosure. In accordance with some embodiments, as shownin FIGS. 2 through 14, an RDL-first (with “RDL” representing“redistribution line”) approach is adopted, with redistributionstructure 50 (FIG. 1A) being formed before placing and bonding dies. Thecorresponding processes are also reflected schematically in the processflow shown in FIG. 28. In accordance with alternative embodiments, anRDL-last approach may be adopted, with the dies placed and bonded first,and then redistribution structure 50 is formed.

FIG. 2 illustrates carrier 102 and release film 104 formed on carrier102. Carrier 102 may be a glass carrier, a silicon wafer, an organiccarrier, or the like. Carrier 102 may have a round top-view shape inaccordance with some embodiments. Release film 104 may be formed of apolymer-based material (such as a Light-To-Heat-Conversion (LTHC)material), which is capable of being decomposed under heat-carryingradiation such as a laser beam, so that carrier 102 may be de-bondedfrom the overlying structures that will be formed in subsequentprocesses. In accordance with some embodiments of the presentdisclosure, release film 104 is formed of an epoxy-based thermal-releasematerial, which is coated onto carrier 102.

A plurality of dielectric layers and a plurality of RDLs are formed overthe release film 104, as shown in FIGS. 2 through 5. Referring to FIG.2, dielectric layer 54 is formed on release film 104. In accordance withsome embodiments of the present disclosure, dielectric layer 54 isformed of a polymer, which may also be a photo-sensitive material suchas polybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or thelike, that may be patterned using a photo lithography process includinga light-exposure process and a development process.

Redistribution Lines (RDLs) 106 are formed over dielectric layer 54 inaccordance with some embodiments. The respective process is illustratedas process 202 in the process flow 200 as shown in FIG. 28. Theformation of RDLs 106 may include forming a metal seed layer (not shown)over dielectric layer 54, forming a patterned mask (not shown) such as aphoto resist over the metal seed layer, and then performing a metalplating process on the exposed seed layer. The patterned mask and theportions of the seed layer covered by the patterned mask are thenremoved, leaving RDLs 106 as shown in FIG. 2. In accordance with someembodiments of the present disclosure, the seed layer includes atitanium layer and a copper layer over the titanium layer. The seedlayer may be formed using, for example, Physical Vapor Deposition (PVD)or a like process. The plating may be performed using, for example, anelectrochemical plating process or an electro-less plating process.

Referring to FIG. 3, dielectric layer 108 is formed on RDLs 106. Therespective process is illustrated as process 204 in the process flow 200as shown in FIG. 28. The bottom surface of dielectric layer 108 is incontact with the top surfaces of RDLs 106 and dielectric layer 54. Inaccordance with some embodiments of the present disclosure, dielectriclayer 108 is formed of a polymer, which may be a photo-sensitivematerial such as PBO, polyimide, BCB, or the like. Alternatively,dielectric layer 108 may include a non-organic dielectric material suchas silicon oxide, silicon nitride, silicon carbide, silicon oxynitride,or the like. Dielectric layer 108 is then patterned to form openings 110therein. Some portions of RDLs 106 are exposed through the openings 110in dielectric layer 108.

Next, referring to FIG. 4, RDLs 112 are formed to connect to RDLs 106.The respective process is illustrated as process 206 in the process flow200 as shown in FIG. 28. RDLs 112 include metal traces (metal lines)over dielectric layer 108. RDLs 112 also include vias extending into theopenings 110 in dielectric layer 108. RDLs 112 may also be formedthrough a plating process, wherein each of RDLs 112 includes a seedlayer (not shown) and a plated metallic material over the seed layer. Inaccordance with some embodiments, the formation of RDLs 112 may includedepositing a blanket metal seed layer extending into the via openings,and forming and patterning a first plating mask (such as photo resist),with openings formed over and joining the via openings. A platingprocess is then performed to plate a metallic material, which fullyfills the via openings 110 (FIG. 3), and has some portions higher thanthe top surface of dielectric layer 108. The first plating mask is thenremoved.

The metal seed layer and the plated material may be formed of the samematerial or different materials. The metallic material in RDLs 112 mayinclude a metal or a metal alloy including copper, aluminum, tungsten,or alloys thereof. RDLs 112 include RDL lines (also referred to astraces or trace portions) 112L and via portions (also referred to asvias) 112V, wherein trace portions 112L are over dielectric layer 108,and via portions 112V are in dielectric layer 108. Since trace portions112L and via portions (also referred to as vias) 112V are formed in asame plating process, there is no distinguishable interface between vias112V and the corresponding overlying trace portions 112L. Also, each ofvias 112V may have a tapered profile, with the upper portions wider thanthe corresponding lower portions.

Further referring to FIG. 4, conductive bumps 114 are formed on RDLs112. The respective process is illustrated as process 208 in the processflow 200 as shown in FIG. 28. It is appreciated that although one RDLlayer 112 is illustrated in the example embodiments as shown, there maybe more RDL layers formed over and electrically connecting to RDL layer112. The subsequent formation process is related to the bonding schemefor bonding device dies MD1 (FIG. 7) and BD (FIG. 1A), and related towhether device dies are placed facing down or facing up, and whethersolder bonding, direct metal-to-metal bonding, or hybrid bonding isused. Accordingly, although one formation process is discussed as anexample, other formation processes and structures are in the scope ofthe present disclosure.

In accordance with some embodiments, conductive bumps 114 are platedusing a second plating mask, and may be plated using a same metal seedlayer as for plating RDLs 112. Conductive bumps 114 may comprise copper,nickel, gold, or the like. After conductive bumps 114 are plated, thesecond plating mask is removed, followed by an etching process to removethe exposed portions of the metal seed layer, which was previouslycovered by the second plating mask and the plated RDLs 112. Theremaining portions of the metal seed layer are also considered as beingparts of RDLs 112. Redistribution structure 50 is thus formed.

Next, as shown in FIG. 5, dielectric layer 116 is formed. The respectiveprocess is illustrated as process 210 in the process flow 200 as shownin FIG. 28. A planarization process may be performed to level the topsurfaces of conductive bumps 114 and dielectric layer 116. When hybridbonding is to be performed, dielectric layer 116 may comprise asilicon-containing dielectric material such as silicon oxide. Inaccordance with alternative embodiments, conductive bumps 114 may beformed after the formation of dielectric layer 116, and the formationprocess may include forming openings in dielectric layer 116 to revealthe underlying RDLs 112, and then forming conductive bumps 114. Thecorresponding dielectric layer 116 may comprise an organic material suchas PBO, polyimide, BCB, or the like, or an inorganic dielectric materialsuch as silicon oxide, silicon nitride, silicon oxynitride, or the like.The formation process also include forming a metal seed layer, forming aplating mask, plating a metallic material, removing the plating mask,and then etching undesirable portions of the metal seed layer.

Next, as shown in FIG. 6, metal posts 120 are formed. The respectiveprocess is illustrated as process 212 in the process flow 200 as shownin FIG. 28. The formation process may include forming a metal seedlayer, forming a plating mask (not shown, may be a photo resist) overthe metal seed layer, patterning the plating mask to reveal theunderlying metal seed layer, and then plating a metallic material in theopenings in the plating mask. Metal posts 120 are alternatively referredto as through-vias or through-molding vias since they will penetratethrough the subsequently formed encapsulating material (which may be amolding compound). The plated metallic material may be copper or acopper alloy. Metal posts 120 may have substantially vertical andstraight edges. In accordance with alternative embodiments, conductivebumps 114A are not formed in the preceding processes. Rather, they areformed in the same process for forming metal posts 120.

FIG. 7 illustrates the placement/attachment of tier-1 dies, whichincludes memory dies MD1 and bridge dies BD (also refer to FIG. 1A). Therespective process is illustrated as process 214 in the process flow 200as shown in FIG. 28. Bridge dies BD are in an un-illustratedcross-section, and hence are not shown in FIG. 7. In accordance withsome embodiments, tier-1 dies MD1 and BD faces down, and the electricalconnectors 122 in the tier-1 dies MDI and BD are bonded to conductivebumps 114. In accordance with alternative embodiments, for example, asshown in FIGS. 16A, 16B, and 16C, dies MD1 and BD may face up, and theelectrical connectors on the backside of device dies MD1 and BD arebonded to conductive bumps 114.

Memory dies MD1 and bridge dies BD may have electrical connectors 124A(such as metal pads, metal bumps, or the like) pre-formed as portions ofthe respective device die. Electrical connectors 124A are on thebackside of the respective dies. Dielectric layer 126A may also beformed on the back surface of memory dies MD1 and bridge die BD. Inaccordance with alternative embodiments, electrical connectors 124A arenot pre-formed in memory dies MD1 and bridge dies BD. Rather,through-vias 26A extend to an intermediate level between a top surfaceand back surface of semiconductor substrate 20, and the electricalconnectors are formed after memory dies MD1 and bridge die BD areencapsulated, and formed between the process shown in FIG. 8 and theprocess shown in FIG. 9.

Next, tier-1 dies MD1 and BD and metal posts 120 are encapsulated inencapsulant 130, as shown in FIG. 8. The respective process isillustrated as process 216 in the process flow 200 as shown in FIG. 28.Encapsulant 130 fills the gaps between neighboring through-vias 120 andtier-1 dies MD1 and BD. Encapsulant 130 may include a molding compound,a molding underfill, an epoxy, and/or a resin. When formed of moldingcompound, encapsulant 130 may include a base material, which may be apolymer, a resin, an epoxy, or the like, and filler particles in thebase material. The filler particles may be dielectric particles of SiO₂,Al₂O₃, silica, or the like, and may have spherical shapes. Also, thespherical filler particles may have a plurality of different diameters.

A planarization process such as a Chemical Mechanical Polish (CMP) stepor a mechanical grinding step is then performed to thin encapsulant 130,until through-vias 120 and tier-2 dies MD1 and BD are exposed. Due tothe planarization process, the top ends of through-vias 120 aresubstantially level (coplanar) with the top surfaces of electricalconnectors 124A (if pre-formed), and are substantially coplanar with thetop surface of encapsulant 130. Throughout the description, tier-1 diesand encapsulant 130 are collectively referred to reconstructed wafer131.

Referring to FIG. 9, tier-2 dies LD are bonded to tier-1 dies MD1 and BDand through-vias 120 (and to reconstructed wafer 131). The respectiveprocess is illustrated as process 218 in the process flow 200 as shownin FIG. 28. In the illustrated example embodiments, tier-2 dies LD arebonded to tier-1 dies MDI and BD and through-vias 120 directly, with noRDLs therebetween. In accordance with alternative embodiments, anadditional fan-out redistribution structure (not shown) includingdielectric layers and RDLs may be formed on and connecting to tier-1dies MD1 and BD and through-vias 120, and tier-2 dies LD are bonded tothe additional fan-out redistribution structure. Similar to tier-1 dies,electrical connectors 124B and dielectric layers 126B may be pre-formedin tier-2 dies LD, or may be formed in another additional fan-outredistribution structure over tier-2 dies LD.

FIG. 10 illustrates the encapsulation of tier-2 dies LD in encapsulant132, which may be similar to or the same as encapsulant 130. Aplanarization process is then performed to level the top surfaces oftier-2 dies LD and encapsulant 132. The respective process isillustrated as process 220 in the process flow 200 as shown in FIG. 28.Throughout the description, tier-2 dies LD and encapsulant 132 arecollectively referred to reconstructed wafer 133.

In the example embodiments as shown in FIGS. 9 and 10, tier-1 dies arefirst placed and encapsulated to form a reconstructed wafer 131, anddiscrete tier-2 dies are placed on the reconstructed wafer 131 throughdie-to-wafer bonding. A perspective view of the die-to-wafer bondingprocess is shown in FIG. 23, wherein the reconstructed wafer 131includes tier-1 dies MDI and BD and encapsulant 130. Tier-2 dies LD areplaced onto reconstructed wafer 131. FIG. 24 illustrates an alternativeembodiment, in which both of reconstructed wafers 131 and 133 arepre-formed, and reconstructed wafer 133 is bonded to the reconstructedwafer 131 through wafer-to-wafer bonding. Similar to what are shown inFIGS. 23 and 24, tier-3 dies MD3 may also be bonded to tier-2 diesthrough die-to-wafer bonding or wafer-to-wafer bonding.

Referring to FIG. 11, tier-3 dies MD3 are bonded to tier-2 dies LD (andto reconstructed wafer 133). The respective process is illustrated asprocess 222 in the process flow 200 as shown in FIG. 28. In theillustrated example embodiments, tier-3 dies MD3 are bonded to tier-2dies LD directly, with no RDLs in between. In accordance withalternative embodiments, an additional fan-out redistribution structure(not shown) including dielectric layers and RDLs may be formed on andconnecting to tier-2 dies LD, and tier-3 dies MD3 are bonded to theadditional fan-out redistribution structure.

FIG. 12 illustrates the encapsulation of tier-3 dies MD3 in encapsulant134, which may be similar to or the same as encapsulants 130 and/or 132.The respective process is illustrated as process 224 in the process flow200 as shown in FIG. 28. A planarization process is then performed tolevel the top surfaces of tier-3 dies MD3 and encapsulant 134. Tier-2dies MD3 and encapsulant 134 are collectively referred to reconstructedwafer 135. Throughout the description, the structure includingdielectric layer 54 and the overlying structure is referred to as areconstructed wafer 100, which is also referred to as computing systempackage 100. Next, reconstructed wafer 100 is de-bonded from carrier 102(FIG. 11), for example, by projecting a laser beam on release film 104,so that release film 104 is decomposed. The respective process isillustrated as process 226 in the process flow 200 as shown in FIG. 28.

FIG. 13 illustrates the formation of electrical connectors 142, whichmay include solder regions, metal pads, metal pillars, or combinationsthereof. The respective process is illustrated as process 228 in theprocess flow 200 as shown in FIG. 28. The formation process may includeforming openings in dielectric layer 54, and forming electricalconnectors 142 extending into the openings to contact RDLs 106.

FIG. 14 illustrates the bonding of reconstructed wafer 100 to packagecomponent 144, which may be or may include a printed circuit board, apackage substrate, a silicon interposer, an organic interposer, a powermodule, a socket, or the like. The respective process is illustrated asprocess 230 in the process flow 200 as shown in FIG. 28. Underfill 146is dispensed into the gap between reconstructed wafer 100 and packagecomponent 144. Package 148 is thus formed. In accordance with someembodiments, a connector 152, which may be an adapter, a socket(including pin holes to insert pins), or the like, may be formed inpackage 148, for example, attached to package component 144, so that thecircuits in package 148 may be electrically connected to externalcomponents.

In accordance with some embodiments, the entire reconstructed wafer 100that is not sawed is bonded to package component 144, and is included inthe resulting package 148. Accordingly, reconstructed wafer 100 inpackage 148 may have a round top view, similar to what are shown inFIGS. 23 and 24. In accordance with alternative embodiments,reconstructed wafer 100 is trimmed to remove the portions that have nodevice dies and conductive lines, while the parts including devices andconductive line containing parts are not trimmed. In accordance with yetalternative embodiments, reconstructed wafer 100 is sawed along scribelines 141 (FIG. 13) into a plurality of identical packages, eachincluding all of the illustrated multiple device dies as shown in FIG.13, and one of the identical package is used to form the package as inFIG. 14.

FIG. 27 illustrates an amplified view of region 150 in FIG. 14. As shownin FIG. 27, encapsulant 130 includes base material 130A and fillerparticles 130B in base material 130A. Encapsulant 132 includes basematerial 132A and filler particles 132B in base material 130A.Encapsulant 134 includes base material 134A and filler particles 134B inbase material 134A. Since no planarization is performed on the bottomsurface of encapsulant 130, the spherical particles 130B that are incontact with redistribution structure 50 are rounded, with the roundedsurfaces in contact with redistribution structure 50. The portions ofencapsulant 130 in contact with encapsulant 132 (or the additionalredistribution structure (if any) have been planarized in the step shownin FIG. 8. Accordingly. The spherical particles 130B at the top surfaceof encapsulant 130 are partially polished during the planarization, andhence will have substantially planar top surfaces. Similar, in each ofencapsulant 132 and 134, the spherical particles 132B/134B at the bottomsurfaces are not polished, and are spherical, while the sphericalparticles 132B/134B at the top surfaces are polished, and are partialspherical particles with round bottom surface and planar top surfaces.

FIGS. 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B, 17C, 19A, 19B, 20A, 20B,21A, 21B, 22A, and 22B illustrate the cross-sectional views of computingsystem packages 100 in accordance with alternative embodiments. Theseembodiments are similar to the embodiments shown in FIGS. 1A, 1B, 1C,1D, 1E, 1F, and 1G (and FIGS. 2 through 13), with some parts modified.Accordingly, the discussion provided in preceding embodiments may alsobe applied to these embodiments whenever applicable.

The embodiments shown in FIGS. 15A, 15B, 15C, 16A, 16B, 16C, 17A, 17B,and 17C may also be obtained from the reference cross-sections 1A-1A,1F-1F, and 1G-1G in FIGS. 1B and 1C.

FIGS. 15A, 15B, and 15C illustrate computing system package 100 inaccordance with some embodiments. These embodiments are similar to theembodiments in FIG. 1A, 1B, 1C, 1D, 1E, 1F, and 1G (which is also thestructure in FIG. 13), except that in FIG. 13, each of the memory diesMD1 and MD3 is a single memory die, while in the embodiments in FIGS.15A, 15B, and 15C, memory stacks MD1′ and MD3′ may be used, whichincludes a plurality of stacked memory dies MD1 and MD3, respectively.The plurality of memory dies MD1 may be interconnected through thethrough-substrate vias formed therein. Tie-1 dies, tier-2 dies, andtier-3 dies face down in accordance with these embodiments. Tier-3 diesMD3 may also be parts of die stacks MD3′.

FIGS. 16A, 16B, and 16C illustrate computing system package 100 inaccordance with some embodiments. These embodiments are similar to theembodiments in FIG. 1A, 1B, 1C, 1D, 1E, 1F, and 1G (which is also thestructure in FIG. 13), except that in FIG. 13, tier-1 dies MD1 and BDface down, while in the embodiments in FIGS. 16A, 16B, and 16C, tier-1dies MD1 and BD face up. Tier-2 dies LD and tier-3 dies MD3 still facedown.

FIGS. 17A, 17B, and 17C illustrate the computing system package 100 inaccordance with some embodiments. These embodiments are similar to theembodiments in FIGS. 15A, 15B, and 15C, except that in FIGS. 15A, 15B,and 15C, the memory dies MD1 and bridge dies BD face down, while in theembodiments in FIGS. 17A, 17B, and 17C, the memory dies MD1 and bridgedies BD face up. Tier-2 dies LD and tier-3 dies MD3 still face down.

FIGS. 18A and 18B illustrate a top view and a bottom view, respectively,of a computing system package 100 in accordance with some embodiments,these embodiments are similar to the embodiments as shown in FIGS. 1Band 1C, except that besides bridge dies BD (marked as BD1) thatinterconnect four logic dies, bridge dies BD (marked as BD2) may beadded to interconnect two neighboring logic dies LD. In accordance withalternative embodiments, the bridge dies BD1 are not formed, whilebridge dies BD2 are formed. In subsequent FIGS. 19A, 19B, 20A, 20B, 21A,21B, 22A, and 22B, the figures whose figure numbers including letter “A”are obtained from the reference cross-section A-A in FIGS. 18A and 18B,and the figures whose figure numbers including letter “B” are obtainedfrom the reference cross-section B-B in FIGS. 18A and 18B.

FIGS. 19A and 19B illustrate computing system package 100 in accordancewith some embodiments. These embodiments are similar to the embodimentsin FIGS. 1A, 1B, 1C, 1D, 1E, 1F, and 1G (which is also the structure inFIG. 13), except bridge dies BD2 are added, and each of the illustratedbridge dies BD2 interconnects two tier-2 dies LD, rather thaninterconnects four tier-2 dies LD as bridge dies BD1. The memory dies intier-1 and tier-3 are single memory dies.

FIGS. 20A and 20B illustrate computing system package 100 in accordancewith some embodiments. These embodiments are similar to the embodimentsin FIGS. 19A and 19B, except in FIGS. 20A and 20B, memory die stacksMD1′ and MD3′ are used.

FIGS. 21A and 21B illustrate computing system package 100 in accordancewith some embodiments. These embodiments are similar to the embodimentsin FIGS. 19A and 19B, except that in FIGS. 19A and 19B, tier-1 dies MD1and BD1 face down, while in FIGS. 21A and 21B, tier-1 dies MD1 and BD1face up.

FIGS. 22A and 22B illustrate computing system package 100 in accordancewith some embodiments. These embodiments are similar to the embodimentsin FIGS. 20A and 20B, except that in FIGS. 20A and 20B, bridge dies BDand tier-1 dies MD1 in memory die stacks MD1′ face down, while in inFIGS. 22A and 22B, bridge dies BD and tier-1 dies MD1 in memory diestacks MD1′ face up.

The embodiments of the present disclosure have some advantageousfeatures. By forming computing system packages including three tiers,with the middle tier having logic dies, and memory dies in the upper andlower tiers, logic dies have shortest paths to the memory dies. Bridgedies are formed to interconnect neighboring logic dies. The scalabilityof the system is improved due to the adoption of arrays of logic dies,memory dies, and bridge dies. The computing efficiency may be improved,the bandwidth of the system may be increased, and the latency may bereduced.

In accordance with some embodiments of the present disclosure, a methodcomprises forming a reconstructed wafer, which comprises forming aredistribution structure over a carrier; bonding a first plurality ofmemory dies over the redistribution structure; bonding a plurality ofbridge dies over the redistribution structure; bonding a plurality oflogic dies over the first plurality of memory dies and the plurality ofbridge dies, wherein each of the plurality of bridge dies interconnects,and is overlapped by corner regions of, four of the plurality of logicdies; and bonding a second plurality of memory dies over the pluralityof logic dies, wherein the plurality of logic dies form a first array,and the second plurality of memory dies form a second array. Inaccordance with an embodiment, the method further comprises bonding apackage component to the reconstructed wafer to form an additionalpackage. In accordance with an embodiment, at a time of the packagecomponent is bonded to the reconstructed wafer, the reconstructed wafercomprises the first array and the second array. In accordance with anembodiment, the method further comprises attaching a socket to theadditional package, wherein at a time after the socket is attached, thereconstructed wafer comprises both of the first array and the secondarray. In accordance with an embodiment, the method further comprisesencapsulating the first plurality of memory dies and the plurality ofbridge dies in a first encapsulant; encapsulating the plurality of logicdies in a second encapsulant; and encapsulating the second plurality ofmemory dies in a third encapsulant. In accordance with an embodiment,the reconstructed wafer is free from logic dies in the first encapsulantand the third encapsulant, and free from memory dies in the secondencapsulant. In accordance with an embodiment, the plurality of logicdies have bottom surfaces in physical contact with a top surface of thefirst encapsulant. In accordance with an embodiment, the secondencapsulant is encapsulated over, and is in physical contact with, thefirst encapsulant. In accordance with an embodiment, the first pluralityof memory dies are identical to each other, the plurality of logic diesare identical to each other, and the second plurality of memory dies areidentical to each other. In accordance with an embodiment, the pluralityof logic dies are bonded to the first plurality of memory dies throughhybrid bonding. In accordance with an embodiment, the bonding theplurality of logic dies over the first plurality of memory dies and theplurality of bridge dies is performed through die-to-wafer bonding. Inaccordance with an embodiment, the bonding the plurality of logic diesover the first plurality of memory dies and the plurality of bridge diesis performed through a wafer-to-wafer bonding process comprisingencapsulating the first plurality of memory dies and the plurality ofbridge dies to form a first reconstructed wafer; encapsulating theplurality of logic dies to form a second reconstructed wafer; andbonding the second reconstructed wafer to the first reconstructed waferthrough wafer-to-wafer bonding.

In accordance with some embodiments of the present disclosure, a packagecomprises a redistribution structure; a first plurality of memory diesover the redistribution structure; a plurality of bridge dies over theredistribution structure; a plurality of logic dies over the firstplurality of memory dies and the plurality of bridge dies, wherein eachof the plurality of bridge dies interconnects, and is overlapped bycorner regions of, at least two of the plurality of logic dies, whereinthe plurality of logic dies are identical to each other; and a secondplurality of memory dies over and bonded to the plurality of logic dies,wherein the plurality of logic dies form a first array, and the secondplurality of memory dies form a second array. In accordance with anembodiment, the first plurality of memory dies are identical to eachother, the second plurality of memory dies are identical to each other,the plurality of logic dies are identical to each other, and theplurality of bridge dies are identical to each other. In accordance withan embodiment, the plurality of bridge dies further comprise capacitorstherein. In accordance with an embodiment, the package further comprisesa first encapsulant encapsulating the first plurality of memory diestherein; a second encapsulant encapsulating the plurality of logic diestherein, wherein the plurality of logic dies have bottom surfacescontacting a top surface of the first encapsulant; and a thirdencapsulant encapsulating the second plurality of memory dies therein.In accordance with an embodiment, the third encapsulant is in physicalcontact with the second encapsulant.

In accordance with some embodiments of the present disclosure, a packagecomprises a reconstructed wafer, which comprises a redistributionstructure comprising a plurality of redistribution lines; a plurality ofbridge dies over and bonded to the redistribution structure; a pluralityof logic dies over and bonded to the plurality of bridge dies, whereinat least one of the plurality of bridge dies is bonded to corner regionsof four of the plurality of logic dies; and a second plurality of memorydies over and bonded to the plurality of logic dies, wherein the secondplurality of memory dies are bonded to the plurality of logic dies. Inaccordance with an embodiment, the package further comprises a packagecomponent bonding to the reconstructed wafer. In accordance with anembodiment, the package further comprises a socket bonding to thepackage component.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a reconstructedwafer comprising: forming a redistribution structure over a carrier;bonding a first plurality of memory dies over the redistributionstructure; bonding a plurality of bridge dies over the redistributionstructure; bonding a plurality of logic dies over the first plurality ofmemory dies and the plurality of bridge dies, wherein each of theplurality of bridge dies interconnects, and is overlapped by cornerregions of, four of the plurality of logic dies; and bonding a secondplurality of memory dies over the plurality of logic dies, wherein theplurality of logic dies form a first array, and the second plurality ofmemory dies form a second array.
 2. The method of claim 1 furthercomprising: bonding a package component to the reconstructed wafer toform an additional package.
 3. The method of claim 2, wherein at a timeof the package component is bonded to the reconstructed wafer, thereconstructed wafer comprises the first array and the second array. 4.The method of claim 3 further comprising attaching a socket to theadditional package, wherein at a time after the socket is attached, thereconstructed wafer comprises both of the first array and the secondarray.
 5. The method of claim 1 further comprising: encapsulating thefirst plurality of memory dies and the plurality of bridge dies in afirst encapsulant; encapsulating the plurality of logic dies in a secondencapsulant; and encapsulating the second plurality of memory dies in athird encapsulant.
 6. The method of claim 5, wherein the reconstructedwafer is free from logic dies in the first encapsulant and the thirdencapsulant, and free from memory dies in the second encapsulant.
 7. Themethod of claim 5, wherein the plurality of logic dies have bottomsurfaces in physical contact with a top surface of the firstencapsulant.
 8. The method of claim 5, wherein the second encapsulant isencapsulated over, and is in physical contact with, the firstencapsulant.
 9. The method of claim 1, wherein the first plurality ofmemory dies are identical to each other, the plurality of logic dies areidentical to each other, and the second plurality of memory dies areidentical to each other.
 10. The method of claim 1, wherein theplurality of logic dies are bonded to the first plurality of memory diesthrough hybrid bonding.
 11. The method of claim 1, wherein the bondingthe plurality of logic dies over the first plurality of memory dies andthe plurality of bridge dies is performed through die-to-wafer bonding.12. The method of claim 1, wherein the bonding the plurality of logicdies over the first plurality of memory dies and the plurality of bridgedies is performed through a wafer-to-wafer bonding process comprising:encapsulating the first plurality of memory dies and the plurality ofbridge dies to form a first reconstructed wafer; encapsulating theplurality of logic dies to form a second reconstructed wafer; andbonding the second reconstructed wafer to the first reconstructed waferthrough wafer-to-wafer bonding.
 13. A package comprising: aredistribution structure; a first plurality of memory dies over theredistribution structure; a plurality of bridge dies over theredistribution structure; a plurality of logic dies over the firstplurality of memory dies and the plurality of bridge dies, wherein eachof the plurality of bridge dies interconnects, and is overlapped bycorner regions of, at least two of the plurality of logic dies; and asecond plurality of memory dies over and bonded to the plurality oflogic dies, wherein the plurality of logic dies form a first array, andthe second plurality of memory dies form a second array.
 14. The packageof claim 13, wherein the first plurality of memory dies are identical toeach other, the second plurality of memory dies are identical to eachother, the plurality of logic dies are identical to each other, and theplurality of bridge dies are identical to each other.
 15. The package ofclaim 13, wherein the plurality of bridge dies further comprisecapacitors therein.
 16. The package of claim 13 further comprising: afirst encapsulant encapsulating the first plurality of memory diestherein; a second encapsulant encapsulating the plurality of logic diestherein, wherein the plurality of logic dies have bottom surfacescontacting a top surface of the first encapsulant; and a thirdencapsulant encapsulating the second plurality of memory dies therein.17. The package of claim 16, wherein the third encapsulant is inphysical contact with the second encapsulant.
 18. A package comprising:a reconstructed wafer comprising: a redistribution structure comprisinga plurality of redistribution lines; a plurality of bridge dies over andbonded to the redistribution structure; a plurality of logic dies overand bonded to the plurality of bridge dies, wherein at least one of theplurality of bridge dies is bonded to corner regions of four of theplurality of logic dies; and a second plurality of memory dies over andbonded to the plurality of logic dies, wherein the second plurality ofmemory dies are bonded to the plurality of logic dies.
 19. The packageof claim 18 further comprising a package component bonding to thereconstructed wafer.
 20. The package of claim 19 further comprising asocket bonding to the package component.